Embodiments of the inventive concept relate generally to electronic memory technologies. More particularly, embodiments of the inventive concept relate to resistive memory devices and methods of controlling refresh operations in resistive memory devices.
Semiconductor memory devices can be roughly divided into two categories according to whether they retain stored data when disconnected from power. These categories include volatile memory devices, which lose stored data when disconnected from power, and nonvolatile memory devices, which retain stored data when disconnected from power. Examples of volatile memory devices include dynamic random access memory (DRAM) and static random access memory (SRAM), and examples of nonvolatile memory devices include flash memory, read only memory (ROM), and resistive memory.
A resistive memory comprises a material that changes resistance on the magnitude and/or direction of current or voltage applied thereto. Examples of resistive memory devices include phase-change random access memory (PRAM), which stores data using a phase-change material, resistive random access memory (RRAM), which stores data using a variable-resistance material such as complex metal oxide, and magnetic random access memory (MRAM), which stores data using a ferroelectric material.
Although resistive memory devices are capable of retaining stored data when disconnected from power, the data may nevertheless become corrupted through the passage of time, changes in the environment, or repeated reprogramming Unfortunately, this tends to decrease the reliability of the resistive memory devices.